The object of the present invention is the use of 5-aryl-1,3,3-trimethyl-2-methylene-indoline derivatives as well as their physiologically tolerated salts with organic or inorganic acids as dye precursors in dyeing agents for fibers, especially of human hair, it being possible, if desired, to decolorize the dyeing obtained gently at a convenient later time. A further object of the invention are 5-aryl-1,3,3-trimethyl-2-methylene-indoline derivatives, as well as a method for their synthesis.
From the Chemical Abstract No. 1976:462913 of the Russian publication Khimiya Geterotsiklicheskikh Soedinenii 1976, pages 497–499, a method for the synthesis of 5-phenyl-1,3,3-trimethyl-2-methylene-indoline and 4-methoxyphenyl-1,3,3-trimethyl-2-methylene-indoline is known, which starts out from a corresponding arylhydrazine derivative. Since the corresponding arylhydrazine must first be synthesized for each aryl modification for this method the latter is rather expensive and unsuitable for the parallel synthesis of structurally related 5-aryl-1,3,3-trimethyl-2-methylene-indoline derivatives.